I explored how these experts dealt with geological, ecological and climatological changes that might occur over the coming millennia.

Now, though, I'm going to take a step back and think about deep time — our very distant future — in a more holistic, speculative and global way. I do this because of my feeling that something about our collective experience of time is now undergoing a profound transformation.

A look at a few notably longsighted ventures that have already sprouted up around the world can give us a sense of this transformation's character.

Books like Gregory Benford's Deep Time: How Humanity Communicates Across the Millennia, Martin J.S. Rudwick's Scenes from Deep Time, Daniel Lord Smail's On Deep History And The Brain, and Stephen Jay Gould's Time's Arrow, Time's Cycle have compelled us to envision distant pasts and futures.

Deep time thinking has been fostered in the Finnish Society of Bioart's Deep Time of Life and Arttrips to ancient paintings found on 550-million-year-old rocks located atop Finnish Lapland's the two-billion-year-old bedrock. It has also been fostered in New Zealand in A Walk Through Deep Time, as walkers "followed a farm fenceline of 457 metres to represent 4.57 billion years" alongside "astronomers, geologists, physicists and biologists as well as matauranga Maori practitioners, philosophers, artists, teachers and a wider public."

At my own academic home base, Cornell University, an archaeology course has challenged students to imagine "the Cornell campus as it would look 1,000 years from now." A course named Global Weirding: Climate Change & Culturehas challenged freshmen to explore how philosophers' musings on "awe" and "the sublime" could alter how we view climate change, the Anthropocene and deep time. And Cornell Cinema has shown Michael Madsen's 2010 Into Eternity, a documentary film about Finland's nuclear waste's multi-millennial futures.

Climate change and sustainability debates have meanwhile nudged entire populations toward thinking inter-generationally across centuries and, sometimes, even across millennia. Debates about biodiversity and (human) extinction have laid bare the potential irreversibility of today's environmental problems. And high-level nuclear waste's remarkably long-term risks have led to the establishment of regulations — as in the United States' now-inactive Yucca Mountain repository project — that have drawn legal rules one million years into the future.

In short, engaging with such radically long-term timespans is no longer just for the astrophysicists, theologians, paleontologists, geologists, evolutionary biologists, or archaeologists among us. It has become our collective task.

In what is increasingly called the Anthropocene, we must all now — to borrow words from anthropologist Tim Ingold — refine our understanding of how in "the perspective of millions of years, the duration of our lived experience, of 'our time,' appears utterly inconsequential." We must, to quote anthropologist Richard Irvine, "learn to envisage gradual processes occurring over chronologies that leave the time-perspective of a human life negligible — even if our effects as a species are far from negligible."

Deep time thinking invites us to imagine how our planet might look a decade from now, a century from now, a millennium from now — or even one million millennia from now. It invites us to think holistically about futures near and distant.

But make no mistake. This does not mean we can shirk short-term responsibilities. Poverty, terrorism, war, disease, inequality and corruption are still most urgent problems that merit the utmost attention. What it does mean, though, is that we must have the backbone to look these enormous spans of time in the eye. We must have the courage to accept our responsibility as our planet's — and our descendants' — caretakers, millennium in and millennium out, without cowering before the magnitude of our challenge.

Deep time thinking is about thinking big-picture in a moment in which, to quote PayPal founder and avowed libertarian Peter Thiel, America is growing "very hostile to big ideas" and in which ambitious projects like "the Apollo program are quite unthinkable today." It is about putting the fearful politics of denial aside and dreaming big — imagining new utopias, embarking upon ambitious projects, embracing our country's open futures — in a moment in which some ask "Has America Lost Its Ability To Dream Big?"

Vincent F. Ialenti is a U.S. National Science Foundation Graduate Research Fellow and a PhD Candidate in Cornell University's Department of Anthropology. He holds an MSc in "Law, Anthropology & Society" from the London School of Economics.